// Copyright (c) 2008-2010, Arne Claus
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification, are permitted provided that the 
// following conditions are met:
//
// - Redistributions of source code must retain the above copyright notice, this list of conditions and the following 
//   disclaimer.
// - Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following 
//   disclaimer in the documentation and/or other materials provided with the distribution.
// - Neither the name Arne Claus nor the names of any contributors may be used to endorse or promote products
//   derived from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, 
// INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE 
// USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#ifndef __INCLUDED_CBL_SINGLETON_H__
#define __INCLUDED_CBL_SINGLETON_H__

#include "CBL_Memory.h"
#include "CBL_Debug.h"

CB_NAMESPACE_START

// -------------------------------------------------------------------------------------------------
//	Singleton base class
//	To declare a class as singleton, perform the following steps:
//	- derive from CSingleton<YourClass>
//	- add "CBL_SINGLETON_PRIVATE(YourClass)" to your class
//	- declare your constructor and destructor as private
// -------------------------------------------------------------------------------------------------

template<typename TSingletonClass>
class CSingleton
{
public:
	
	static CB_FORCEINLINE TSingletonClass& CB_INLINE_ATTR CreateInstance()
	{
		if (!IsValid())
			GetInstanceRef() = new TSingletonClass();
		
		return GetInstance();
	}
	
	// -----------------------------------------------------------------------------------------------------------------
	
	static CB_FORCEINLINE void CB_INLINE_ATTR Release()					
	{ 
		if (IsValid()) 
			delete GetInstanceRef(); 
	}
	
	// -----------------------------------------------------------------------------------------------------------------
	
	static CB_FORCEINLINE TSingletonClass& CB_INLINE_ATTR GetInstance()	
	{ 
		Debug::Assert(IsValid(), "GetInstance() called on uninitialized singleton.");
		return *GetInstanceRef(); 
	}
	
	// -----------------------------------------------------------------------------------------------------------------
	
	static CB_FORCEINLINE bool CB_INLINE_ATTR IsValid()
	{
		return GetInstanceRef() != NULL;
	}
	
private:
	
	CSingleton(const CSingleton&);					// not implemented on purpose
	CSingleton& operator = (const CSingleton&);		// not implemented on purpose
	
protected:
	
	CSingleton() {}
	virtual ~CSingleton()
	{ 
		GetInstanceRef() = NULL; 
	}

private:

	DERIVED_API static TSingletonClass*& GetInstanceRef()
	{
		static TSingletonClass* pInstance = NULL;
		return pInstance;
	}
};

// -------------------------------------------------------------------------------------------------

#define CBL_SINGLETON_PRIVATE(_ClassName) friend class CSingleton<_ClassName>

// -------------------------------------------------------------------------------------------------

CB_NAMESPACE_END

#endif